dibbler/sqlalchemy/dialects/postgresql/json.py

# postgresql/json.py
# Copyright (C) 2005-2017 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
from __future__ import absolute_import

import json
import collections

from .base import ischema_names, colspecs
from ... import types as sqltypes
from ...sql import operators
from ...sql import elements
from ... import util

__all__ = ('JSON', 'JSONB')

idx_precedence = operators._PRECEDENCE[operators.json_getitem_op]

ASTEXT = operators.custom_op(
    "->>", precedence=idx_precedence, natural_self_precedent=True,
    eager_grouping=True
)

JSONPATH_ASTEXT = operators.custom_op(
    "#>>", precedence=idx_precedence, natural_self_precedent=True,
    eager_grouping=True
)


HAS_KEY = operators.custom_op(
    "?", precedence=idx_precedence, natural_self_precedent=True,
    eager_grouping=True
)

HAS_ALL = operators.custom_op(
    "?&", precedence=idx_precedence, natural_self_precedent=True,
    eager_grouping=True
)

HAS_ANY = operators.custom_op(
    "?|", precedence=idx_precedence, natural_self_precedent=True,
    eager_grouping=True
)

CONTAINS = operators.custom_op(
    "@>", precedence=idx_precedence, natural_self_precedent=True,
    eager_grouping=True
)

CONTAINED_BY = operators.custom_op(
    "<@", precedence=idx_precedence, natural_self_precedent=True,
    eager_grouping=True
)


class JSONPathType(sqltypes.JSON.JSONPathType):
    def bind_processor(self, dialect):
        super_proc = self.string_bind_processor(dialect)

        def process(value):
            assert isinstance(value, collections.Sequence)
            tokens = [util.text_type(elem)for elem in value]
            value = "{%s}" % (", ".join(tokens))
            if super_proc:
                value = super_proc(value)
            return value

        return process

    def literal_processor(self, dialect):
        super_proc = self.string_literal_processor(dialect)

        def process(value):
            assert isinstance(value, collections.Sequence)
            tokens = [util.text_type(elem)for elem in value]
            value = "{%s}" % (", ".join(tokens))
            if super_proc:
                value = super_proc(value)
            return value

        return process

colspecs[sqltypes.JSON.JSONPathType] = JSONPathType


class JSON(sqltypes.JSON):
    """Represent the PostgreSQL JSON type.

    This type is a specialization of the Core-level :class:`.types.JSON`
    type.   Be sure to read the documentation for :class:`.types.JSON` for
    important tips regarding treatment of NULL values and ORM use.

    .. versionchanged:: 1.1 :class:`.postgresql.JSON` is now a PostgreSQL-
       specific specialization of the new :class:`.types.JSON` type.

    The operators provided by the PostgreSQL version of :class:`.JSON`
    include:

    * Index operations (the ``->`` operator)::

        data_table.c.data['some key']

        data_table.c.data[5]


    * Index operations returning text (the ``->>`` operator)::

        data_table.c.data['some key'].astext == 'some value'

    * Index operations with CAST
      (equivalent to ``CAST(col ->> ['some key'] AS <type>)``)::

        data_table.c.data['some key'].astext.cast(Integer) == 5

    * Path index operations (the ``#>`` operator)::

        data_table.c.data[('key_1', 'key_2', 5, ..., 'key_n')]

    * Path index operations returning text (the ``#>>`` operator)::

        data_table.c.data[('key_1', 'key_2', 5, ..., 'key_n')].astext == \
'some value'

    .. versionchanged:: 1.1  The :meth:`.ColumnElement.cast` operator on
       JSON objects now requires that the :attr:`.JSON.Comparator.astext`
       modifier be called explicitly, if the cast works only from a textual
       string.

    Index operations return an expression object whose type defaults to
    :class:`.JSON` by default, so that further JSON-oriented instructions
    may be called upon the result type.

    Custom serializers and deserializers are specified at the dialect level,
    that is using :func:`.create_engine`.  The reason for this is that when
    using psycopg2, the DBAPI only allows serializers at the per-cursor
    or per-connection level.   E.g.::

        engine = create_engine("postgresql://scott:tiger@localhost/test",
                                json_serializer=my_serialize_fn,
                                json_deserializer=my_deserialize_fn
                        )

    When using the psycopg2 dialect, the json_deserializer is registered
    against the database using ``psycopg2.extras.register_default_json``.

    .. seealso::

        :class:`.types.JSON` - Core level JSON type

        :class:`.JSONB`

    """

    astext_type = sqltypes.Text()

    def __init__(self, none_as_null=False, astext_type=None):
        """Construct a :class:`.JSON` type.

        :param none_as_null: if True, persist the value ``None`` as a
         SQL NULL value, not the JSON encoding of ``null``.   Note that
         when this flag is False, the :func:`.null` construct can still
         be used to persist a NULL value::

             from sqlalchemy import null
             conn.execute(table.insert(), data=null())

         .. versionchanged:: 0.9.8 - Added ``none_as_null``, and :func:`.null`
            is now supported in order to persist a NULL value.

         .. seealso::

              :attr:`.JSON.NULL`

        :param astext_type: the type to use for the
         :attr:`.JSON.Comparator.astext`
         accessor on indexed attributes.  Defaults to :class:`.types.Text`.

         .. versionadded:: 1.1

         """
        super(JSON, self).__init__(none_as_null=none_as_null)
        if astext_type is not None:
            self.astext_type = astext_type

    class Comparator(sqltypes.JSON.Comparator):
        """Define comparison operations for :class:`.JSON`."""

        @property
        def astext(self):
            """On an indexed expression, use the "astext" (e.g. "->>")
            conversion when rendered in SQL.

            E.g.::

                select([data_table.c.data['some key'].astext])

            .. seealso::

                :meth:`.ColumnElement.cast`

            """

            if isinstance(self.expr.right.type, sqltypes.JSON.JSONPathType):
                return self.expr.left.operate(
                    JSONPATH_ASTEXT,
                    self.expr.right, result_type=self.type.astext_type)
            else:
                return self.expr.left.operate(
                    ASTEXT, self.expr.right, result_type=self.type.astext_type)

    comparator_factory = Comparator


colspecs[sqltypes.JSON] = JSON
ischema_names['json'] = JSON


class JSONB(JSON):
    """Represent the PostgreSQL JSONB type.

    The :class:`.JSONB` type stores arbitrary JSONB format data, e.g.::

        data_table = Table('data_table', metadata,
            Column('id', Integer, primary_key=True),
            Column('data', JSONB)
        )

        with engine.connect() as conn:
            conn.execute(
                data_table.insert(),
                data = {"key1": "value1", "key2": "value2"}
            )

    The :class:`.JSONB` type includes all operations provided by
    :class:`.JSON`, including the same behaviors for indexing operations.
    It also adds additional operators specific to JSONB, including
    :meth:`.JSONB.Comparator.has_key`, :meth:`.JSONB.Comparator.has_all`,
    :meth:`.JSONB.Comparator.has_any`, :meth:`.JSONB.Comparator.contains`,
    and :meth:`.JSONB.Comparator.contained_by`.

    Like the :class:`.JSON` type, the :class:`.JSONB` type does not detect
    in-place changes when used with the ORM, unless the
    :mod:`sqlalchemy.ext.mutable` extension is used.

    Custom serializers and deserializers
    are shared with the :class:`.JSON` class, using the ``json_serializer``
    and ``json_deserializer`` keyword arguments.  These must be specified
    at the dialect level using :func:`.create_engine`.  When using
    psycopg2, the serializers are associated with the jsonb type using
    ``psycopg2.extras.register_default_jsonb`` on a per-connection basis,
    in the same way that ``psycopg2.extras.register_default_json`` is used
    to register these handlers with the json type.

    .. versionadded:: 0.9.7

    .. seealso::

        :class:`.JSON`

    """

    __visit_name__ = 'JSONB'

    class Comparator(JSON.Comparator):
        """Define comparison operations for :class:`.JSON`."""

        def has_key(self, other):
            """Boolean expression.  Test for presence of a key.  Note that the
            key may be a SQLA expression.
            """
            return self.operate(HAS_KEY, other, result_type=sqltypes.Boolean)

        def has_all(self, other):
            """Boolean expression.  Test for presence of all keys in jsonb
            """
            return self.operate(HAS_ALL, other, result_type=sqltypes.Boolean)

        def has_any(self, other):
            """Boolean expression.  Test for presence of any key in jsonb
            """
            return self.operate(HAS_ANY, other, result_type=sqltypes.Boolean)

        def contains(self, other, **kwargs):
            """Boolean expression.  Test if keys (or array) are a superset
            of/contained the keys of the argument jsonb expression.
            """
            return self.operate(CONTAINS, other, result_type=sqltypes.Boolean)

        def contained_by(self, other):
            """Boolean expression.  Test if keys are a proper subset of the
            keys of the argument jsonb expression.
            """
            return self.operate(
                CONTAINED_BY, other, result_type=sqltypes.Boolean)

    comparator_factory = Comparator

ischema_names['jsonb'] = JSONB